Sep 7 The Charterhouse Exoplanet Project

Exoplanets are one of the fastest paced areas of astrophysical study of recent times. Almost weekly there are reports of newly discovered exotic and strange words. Only this week have we seen the news that one of our closest stars, Proxima Centauri, has a very high chance of harbouring a world similar to our own, within its habitable zone. Stories such as these captivate the public, and we dream of future vistas like those shown of the iconic Tattooine in the film franchise Star Wars.As an ‘amateur’ astrophysicist my main area of interest when it comes to study, are compact high-energy stellar remnants i.e. black holes, collapsars & magnetars, all very strange and non-intuitive corpses of long dead massive stars. However, in an amateur setting, they are extremely difficult to study, requiring fairly advanced and costly non-optical telescopes. Exoplanets however, can be detected with low tech, budget equipment which puts it right between the crosshairs of amateur accessibility, and this is the core reason why I started the Charterhouse Exoplanet Project.

The project itself was conceived in the winter of 2014. I had recently acquired some time on a 0.5m class telescope housed in the only observatory close to where I live in Somerset, that was open to public use. I’d managed to get this time by helping an initial renovation of the telescope as the 50 year old instrument was pretty dilapidated and in need of some TLC. I’ve done a lot of visual astronomy in the last 12 years, and even though the Charterhouse telescope was a veritable light bucket, I wanted to do something more than just look at pretty things in the sky. At that point I was reminded of my A-Level years, when I was taking the GCSE Astronomy course as an extra to fill some free lesson time I had. The coursework for the GCSE involved a certain amount of ‘practical’ activity which frankly, I struggled to do (at that point I was borrowing a very basic telescope from my school physics teacher to do observations). I thought to myself, this 0.5m telescope, and my allocated time with it, would be much better utilised if I were to open it up to other students who are now in the same position as I was all those years ago. All I needed now, was something to actually base this organisation around. Having had lengthy discussions with a physics colleague of mine (who also happens to be the physics teacher) we reached the conclusion that exoplanet detection, though tricky, would be an ideal activity for the telescope and my limited budget. We started carrying out some very preliminary run-up work with the telescope, tracking accuracy, imaging, focus etc, and found that the telescope really wasn’t up to the job. Bummer! This discovery lead to 18 months of blood, sweat, tears and swearing along with a number of engineering setbacks and other hidden niggles that we hadn’t anticipated at first.

On December 12th 2016, the fully renovated Charterhouse Telescope was officially re-opened (for the 4th time in its life) having basically been rebuilt from the ground up. New mirror coating (almost the best amateur money can buy), new drive motors, new mount bearings, new finder scope, new focus unit and a couple tins of hammerite. We were now ready to start the discovery of new worlds….well, until we were struck by the “astronomers curse”. For those not familiar with the astronomers curse, the number of days of bad weather following an astronomy hardware purchase is proportional to its size. 12ft of newly refurbished telescope amounted to nearly 2 months of solid rain. We didn’t really get a good chance to test everything in its new state until sometime in mid-February 2016. The first object we targeted was the famous Orion Nebula, and it looked fantastic. I can easily say that it was the most fantastic thing I’d ever seen with only the naked eye, so much detail and clarity from the newly coated 18” mirrors. The clear cold skies also helped, the ambient air temperature in the dome reached -5 Celsius that night.

Since that night, we have had a few technical setbacks including the breaking of the mechanism which opens the dome door, which is still to be resolved, that will be our little summer project this year.

In the meantime we are progressing full steam, engaging with schools, and the public, attending astronomy fairs to raise awareness about our project, and exoplanets as a whole. We have been working with a couple of schools providing on-site astronomy activities and observation evenings, which also include visits to the observatory to see what still is a pretty impressive piece of kit. As a branch of our own outreach work, we are partnered with the TWINKLE UK Space mission, which is being run by a group mainly located at UCL who are in the process of designing and constructing an exoplanet hunting satellite which, when launched will be specifically looking at exoplanet atmospheres using spectroscopy.

Spectroscopy is a very important analytical process in astronomy. It literally allows a distant observer to take the fingerprint of a star, and determine its unique composition. It also allows astronomers to determine the speed of moving objects in space. One important use of spectroscopy is for radial velocity detection of exoplanets. This process makes use of the fact that the orbiting planet will tug a little on its parents star, causing it to wobble. This wobble will appear in the spectra of the star as a slight redshift and a slight blueshift, depending where the planet is within its orbit. This method of exoplanet detection requires large advanced telescopes far out of the scope of amateurs, which is why we use photometry. Photometry is a method of measuring the ‘brightness’ of an object and seeing how it varies over time. Exoplanet photometry detects the planet by measuring the relative brightness of the parent star. When the planet passes over the face of the star relative to Earth, there is a measurable dip in its brightness. The resulting graph of brightness over time is called a transit light curve, from which a lot of information about the planet can be extracted.

In proceeding posts, I’ll look at the photometry process, some of the mathematics behind the light curves and look at some of the more weird exoplanets that we know about.

If you would like to keep up to date with the exoplanet project then find us on twitter @ChartExoplanets or on Facebook.